Strict-Sense Nonblocking W-S-W Node Architectures for Elastic Optical Networks

The paper considers optical node architectures for elastic optical networks. They use switching fabric topologies which are similar to the three-stage Clos switching networks. These architectures employ wavelength switching in the first and the third stages, and space switching in the second stage, and are also called W-S-W switching fabrics. In elastic optical networks, the optical spectrum is divided into frequency slot units. One frequency slot unit uses 12.5 GHz of bandwidth and an optical path may use m adjacent frequency slot units. Such connection is called an m-slot connection. For each architecture, strict-sense nonblocking conditions are derived and proved for such m-slot connections. The number of center stage switches and the number of frequency slot units in interstage links are calculated and evaluated. The considered architectures are compared to each other. When the maximum number of frequency slot units that may be used by one connection, is not too high, these architectures can be implemented in practice.